Crystalline microporous material exist naturally in many kinds such as mordenite, ferrierite. Further, many kinds of artificial crystalline microporous material are known such as Zeolite-A, Zeolite-X, ZSM-Z5 (see Japanese patent Kokoku No. 46-10064), and ZSM-11 (see Japanese patent Kokoku No. 53-23280) and so on.
For manufacturing the artificial crystalline microporous material as mentioned above, there has been employed a method commonly referred to as "hydrothermal synthesis method" which includes a mixing step for obtaining alkaline mixture liquid containing silicon dioxide (SiO.sub.2), aluminum oxide, and organic ammonium salt, and a subsequent crystallizing step for crystallizing crystalline microporous material in the inorganic material mixture liquid by means of high-pressure heating.
That is, according to the hydrothermal method, it has been believed that after the preparation of the mixture liquid the crystallizing step by heating needs to be effected with the solid mixture component thereof being in the liquid. Thus, for obtaining the high-temperature and high-pressure conditions needed for the crystallization, it has been necessary to place the mixture liquid in the form of liquid within a high-pressure heating container (autoclave) and then to heat it.
With the conventional hydrothermal synthesis method described above, the high-pressure heating container is expensive. Also, since the inorganic mixture liquid contains alkaline metal oxide or alkaline earth metal oxide as oxide or hydroxide component thereof, the liquid is strongly alkaline. Therefore, for preventing corrosion due to the strong alkaline, it has been necessary for the high-pressure heating container to be made of e.g. stainless steel or to be provided with fluorine resin surface treatment. In these manners, the method involves many factors which may increase the manufacturing costs in terms of the manufacturing installation. In addition, in handling of such strong alkaline mixture liquid as described above, it has been necessary to take some appropriate and sufficient measure for the safety of the worker engaged in this operation. Therefore, the method may be considered as a very expensive synthesis method from the view point of safety of the installation also.
Further, according to the hydrothermal synthesis method, the crystallizing step thereof requires severe reaction conditions of heating the mixture liquid at a high temperature condition normally at 70.degree. C. to 200.degree. C. or even higher in some cases for a long period extended over a few days or even more than 10 days. This too has contributed to further increase in the manufacturing costs.
Still further, in a small-scale research and development too, the use of the strong alkaline mixture liquid under such high-temperature, high-pressure conditions does not allow the use of ordinary glass container. So, there has been a demand for an improved method which allows inexpensive synthesis of crystalline microporous material under milder conditions.
In addition to the above, the crystalline microporous material obtained by the hydrothermal synthesis is in the form of fine particles, which needs to be molded depending on its application. Yet, the crystalline microporous material in the form of fine particles does not have caking force or property. Then, the molding must be effected by either sintering the material under an extremely high temperature or using a binder in combination. For this reason, the sintering under the very high temperature may cause melting of the surface layer of the crystal or the use of binder may cause blocking of the porous structure. Hence, in either case, there results decrease in the ratio of the crystalline microporous structure present in the molded material, i.e. the molded material will suffer decrease in the ratio of the porous structure per unit weight. Consequently, the resultant molded material tends to suffer deterioration in such properties as adsorbent activity, catalyst activity afforded by the porous structure.
Taking the above-described state of the art into consideration, a primary object of the present invention is to provide an improved method which allows inexpensive synthesis of crystalline microporous material under milder reaction conditions. A further object is to provide an inexpensive crystalline microporous material or crystalline microporous molded product obtained by the method. A still further object of the invention is to provide a crystalline microporous material which may achieve superior performance in a variety of applications.